This invention relates to an improved transportation and/or storage container for radioactive substances, especially for irradiated fuel elements from nuclear reactors.
Containers which are used for the transportation and/or storage of spent nuclear elements must safely enclose the radioactivity of such elements and ensure such safe enclosure even in the event of an extreme accident. Such containers not only must shield or prevent exterior emissions of the gamma- and n-radiation being given off by radioactive decomposition reactions of such elements but also must transfer safely to the outside the heat generated by such reactions.
Known containers, as disclosed for example by the German patent OS No. 22 28 026, have open-top thick-walled metallic container bodies closed by a thick metallic removable cover to ensure the necessary strength and shielding against gamma rays. The bodies are provided with exterior cooling ribs or fins and shielding against neutrons.
Commercial requirements for such containers specify that they must withstand severe accidents, such as a fall onto a hard surface from a height of 9 meters, so as to remain tight with no appreciable structural weakening of the container body. In such a fall, the cooling ribs or fins of the container would experience damage.
These prior containers have a number of disadvantages. Among such is the fact that in containers having welded-on or cast-on cooling ribs, there exists the danger in the case of an accident, for example, a container is dropped and cracks or breaks off one or more cooling ribs, that a crack may continue into the container body, representing the tight enclosure of the radioactive substance.